PROJECT SUMMARY Childhood traumatic stress (CTS), resulting from experiences such as abuse and neglect, is a pervasive public health problem with devastating and lasting consequences effecting overall health across the lifespan. Growing evidence shows that the negative effects of CTS are not limited to a single individual and may be transmitted across generations, increasing the risk for behavioral and psychiatric disorders in the offspring. Psychological stress during pregnancy is associated with heightened stress responses, emotional dysregulation, and behavioral problems in infancy and early childhood potentially making it a key mechanism for the intergenerational transmission of trauma. The majority of studies examining maternal psychological stress (MPS) during pregnancy consider the magnitude of stress as the `risk factor' for alterations in offspring development; however, psychological stress, particularly during the prenatal period, is dynamic and variable. Infant neurodevelopment occurs sequentially and is sensitive to environmental influences, meaning that the effect of any insult is likely as much about the timing, as it is the magnitude. As a result, it remains unclear which aspects of stress most strongly impact offspring development ? is it simply the magnitude as previously suggested, or does the trajectory matter as well? Understanding the variability of prenatal factors and their influence on infant neurobiological and psychosocial development is critical to targeting preventive interventions. The goal of this proposal is to explore maternal psychological stress during pregnancy as a mechanism for the intergenerational transmission of childhood traumatic stress. The overall hypothesis is that a history of maternal CTS will increase the amplitude and velocity of MPS trajectories compared to a low-risk group, will predict increased offspring limbic system connectivity and negative affect expression, and that an intervention to reduce MPS in a high-risk sample will alter the observed trajectories. These hypotheses will be tested using a novel methodology that characterizes the longitudinal heterogeneity of psychological symptom data to create MPS trajectories. These trajectories will be used to explore the role of timing and rate of change of MPS on offspring neurobiological and affective development and, further, to test whether these trajectories mediate the effects of CTS on infant development. The specific aims of this proposal are: (1) To characterize the longitudinal heterogeneity of MPS in a sample of women with and without a history of CTS; (2) To examine the effects of heterogeneous longitudinal trajectories in MPS on offspring limbic system and negative affect development in mothers with and without childhood trauma; and (3) (Exploratory) To determine whether an intervention designed to reduce MPS will alter MPS trajectories in a high-risk sample. This study aims to elucidate the importance of trajectories of MPS for offspring brain and affective development, and as a mechanism for intergenerational transmission of CTS. Achieving these goals will provide insight into the best timing for targeted screening and interventions to alter MPS during pregnancy for women with a history of CTS and, thereby, reduce the risk of offspring psychiatric disorders.